Paper detail

Torus feeding and outflow launching in the active nucleus of the Circinus galaxy

Context: Most active galactic nuclei (AGN) are believed to be surrounded by a dusty molecular torus on the parsec scale which is often embedded within a larger circumnuclear disk (CND). AGN are fuelled by the inward transport of material through these structures and can launch multi-phase outflows that influence the host galaxy through AGN feedback. Aims: We use the Circinus Galaxy as a nearby laboratory to investigate the physical mechanisms responsible for feeding the torus and launching a multi-phase outflow in this Seyfert-type AGN, as these mechanisms remain poorly understood. Methods: We analysed observations from the Atacama Large Millimeter/submillimeter Array of the Circinus nucleus at angular resolutions down to 13 mas (0.25 pc). We traced dust and the ionised outflow using 86-665 GHz continuum emission, and studied the morphology and kinematics of the molecular gas. Results: We find that the Circinus CND hosts molecular and dusty spiral arms, two of which connect directly to the torus. We detect inward mass transport along these structures and argue that the non-axisymmetric potential generated by these arms is the mechanism responsible for fuelling the torus. We estimate a feeding rate of 0.3-7.5 M$_{\odot}$yr$^{-1}$, implying that over 88% of the inflowing material is expelled in a multi-phase outflow before reaching the accretion disk. The inferred torus feeding time scale (120 kyr - 2.7 Myr) suggests that variability in AGN activity may be driven by changes in torus feeding. On parsec scales, the ionised outflow is traced by optically thin free-free emission. The outflow is stratified, with a slightly wider opening angle in the molecular phase than in the dusty and ionised components. The ionised outflow is launched or collimated by a warped accretion disk at a radius of r ~ 0.16 pc, and its geometry requires an anisotropic launching mechanism.